Production of motor fuel



June 18, 1946.

E. HERTHEL PRODUCTION OF MOTOR FUEL Filed Aug. 5, 1941 1 HydrocarbonsCondllm'ny More Han/5w' Caron/I fom:

INVENTOR ATTORNEY 4Patented June l8 1946 OFFICE, 4

PRODUCTION OF MOTOR FUEL v Eugene C. Herthel, Flossmoonll., assignor toSinclair Refining Company, New York, N. Y.,

a corporation of Maine Application August 5, 1941, seriai1\ro.4o5,49

4 claims. V (O1. 26o- 6834) This linvention relates to improvements inthe production of motor fuel, vparticularly aviation gasoline, by thealkylation of isobutane with butylenes in the presence of strongsulfuric acid, and in particular, the improvement in such processes bywhich maximum use of isobutane available in cracked stocks is made whileexcess buf tylenes, present in such stocks, are rejectedy in admixturewith normal butane and are available for other purposes. u y

Processes for the production of motor fuel by alkylation of isobutanewith butylenes are known and used. In general, the alkylation is carriedout by intimately admixing isobutane, butylenes and strong sulfuric acidfor a suiiicient period of time'for the reaction to proceed, a largeexcess of isobutane being used'. The hydrocarbon is then separated fromthe a'cid, and lfractionated to separate the alkylate, and also toseparate the excess isobutane which is returned to the alkylationreaction zone.

'I'he four carbon atom hydrocarbons from the three butylenes, isobutaneand butane, in

1 somewhat variable proportions, along with minor amounts of otherhydrocarbons, and form the usual source of butylenes and a sourceof`part of the isobutane. The quantity of butylenes is usuallyconsiderably in excess of the quantity of isobutane, and in many cases,even with isobutane from outside sources, the amount of butylenes inthese cracked stocks is in excess of the amount of isobutane available.Accordingly some of these butylenes must be rejected so that the amountof isobutane and the amount of the butylenes supplied to the alkylationsystem will balance.

'I'he hydrocarbon separated from the acid after the alkylation reactioncontains alkylate, isobutane, normal butane, and other heavier andlighter` hydrocarbons in minor proportions. The alkylate and isobutanemay be recovered by devbutanizing the mixture and treating the bottomsto recover alkylate and deisobutanizing the overhead to recover theisobutane, or may be deisobutanized, with vrecycling of the overhead andtreatment of the bottoms to recover alkylate. It is usually necessary todepropanize the overhead fromthe deisobutanizer to prevent the propanefrom building up in the system. i

In accordance with the present invention,part or all of the BB feed (thefour carbon atom fraction from cracked stocks) is fed to thedeisobutanizer in which the excess isobutane is recovered for return tothe alkylation unit. This deisobutanizer is operated so that a portionof the butylenes is discharged with the bottoms frac- `tion 'andaportion goes overhead with the isobutane, advantage being taken of thefact that the straight jchain butylenes have boiling points in betweenthose of'normal butane and isobutane.

The operation is carried out in the known Way so that the quantity ofbutylenes in, the overhead is that which is required to maintain thebalance Y between the amount of butylene consumed in the alkylationoperation and the available isobutane. Ordinarily, the quantity ofbutylenes supplied to the reaction zone will be slightly greater thanthe total amount of isobutane available, because some of the butylenesare consumed by interreaction' between themselves to producehydrocarbons other than alkylate and somel are removedv as alkylsulfates in the sulfuric acid purged from the system in accordance withordinary procedure. A11 of the BB stock may be charged to thedeisobutanizer, or only a part of it may be so charged. 'I'hus aportion, for example, one-half, may be charged to the deisobutanizerwhile the remainder is charged directly to the alkylation unit or to thedepropanizer ordinarily provided just prior -to the alkylation unit. Theamountv of such stock supplied directly to the alkylation unit and thatsupplied to the deisobutanizer, and the Aquantity of butylenes rejectedin the deisobu- Vtanizer will ordinarily be governed by the totalquantity of isobutane available, including that in the BB stock and thatavailable from outside sources, such as casinghead.

The invention will be. further described in connection with the appendeddrawing, which illustrate's diagrammatically apparatus in which theinvention may be practiced.

In the apparatus'illustrated, incidental equip. ment such as pumps,condensers, valves, reflux lines, etc., have not been illustrated.

The BB stock is supplied to the depropanizer I0, the overhead from whichis used for any desired purpose. The bottoms are split into two streams,one going directly tothe alkylation unit I2 while the other is suppliedto -the deisobutanizer I4. In the alkylation unit, to which bottoms fromthe depropanizer I6, derived as hereafter explained, are also supplied,the hydrocarbons are brought into intimate contact with strong sulfuricacid for a suicient period of time for the alkylation reaction. Themixture of hydrocarbon and acid removed from the alkylation unit issubjected to stratification in the separator I8, the acid being returnedto the alkylation unit `'and the hydrocarbon introduced into thedebutanizer 20. The overhead from the debutanizer. consisting largely ofisobutane and normal butane is supplied to the deisobutanizer I4, whilethe the overhead supplied to the deisobutanizer I4.

The deisobutanizer I4 is operated in the known way, so thatsubstantially all of the isobutane is separated as an overhead productand substantially all of the normal butane and heavy hydrocarbons as abottoms product, while a portion of the butylenes are included in theoverhead and a portion is included in the bottoms, the amount ofbutylenes discarded in the bottoms being such as to maintain the desiredratio of net input of isobutane to butylenes to the alkylation unit.This ratio should be slightly less than 1 to provide the excessbutylenes required to make up for the losses as alkyl sulfate and thelosses due to interreaction oi' the oleilnes. The amount of these losseswill vary, depending upon the conditions maintained during thealkylation, but for any given operation are readily determined so thatthe desired balance can be maintained.

The following tables give typical data for the operation of a plantillustrated inthe drawing and described above, operating to produce a1-kylate from a BB stock and isobutane containing stock from anothersource.

Depropanizer l Debutsnlzer 22 Feed 0.11. Btms Feed 0. H. Btms L .i7 L LLl Li 11.0 11.0% 0.0% 90.0% ma? qu?? 130.0 1827 13.0 1.0 4.2 0.0 5.0 0.07.7 2.5 10.4 0.0 80.4 0.0 46.6 0.0 0.0 0.0 28.0 0.0 42.8 20.5 85.4 0.00.0 V 0.0 0.0 76.0 0.0 100.0

Reactor l2 Debutanizer 20 Feed Prod. 0. H. Btms lag Wag Liq4.1" q 0.071.9 63.4 81.5 0.0 14.4 0.0 0.0 0.0 10.7 11.2 14.4 0.0 y 0.0 22.2 0.0100.0'

Total 1G10 100.0 1G10 11x10 Quant. liqvols.. 838. 0 322. 2 250. s 71.4

Depropanizer 16 Feed 0. H. Btms HC' L 7 L 9' o. we? 1130.6 ula. 104.82.6 0.0 87. 1.. 6.3 0.0 0. N04.. 2.9 0.0 3. n 0.0 0.0 o.

Total 100.0 100.0 100. Quant. liq. vols 288.0 15.4 l 272.

Deisobutanizer 14 Feed from- Total Depro- Debu- Debupaninitanizertanizer Feed 0.11. Btms i Li L L L J7 L .W 0 49,5 4.911 124.0% kazafq0.5 f 1.7 s 10.4 81.5 40.3 sa- 0.0 46.5 0.0 0.0 5.1 6.3 4.0 42s 85.414.4 50.6 2.0 96.0

Total,... l.0 100.0 100.0 100.0 100.0 100.0 Qumt.liq.vols- 05.4 i745250.8 590.7 288.0 302.7

i Includes come propylene or ethylene.

I claim:

l. In the production of motor fuel by the a1'- kylation of isobutanewith butylenes in the presence of a catalyst, the steps of bringing anexcess of isobutane and the butylenes into intimate contact in thepresence of a catalyst, separating the hydrocarbon from the catalyst.and subjecting the hydrocarbon to fractional distillation to recovertherefrom the excess isobutane, introducing into the fractionatingequipment in which the isobutane is separated a hydrocarbon stockcontaining isobutane, normal butane and butylenes derived from crackedstocks, operating said fractionating equipment so that a portion of thebutylenes having boiling points in between those of normal butane andisobutane isy included in the isobutane-containing fraction and aportion in the bottoms fraction, and returning the overhead fraction tothe reaction zone, the amount of --separating a four carbon atomfraction containing isobutane, butane and butylenes from crackingstocks, introducing a portion thereof into a deisobutaniz'er along witha butane and isobutane containing stock removed from the alkylationreaction zone, operating said deisobutanizer to obtain an overheadfraction containing the isobutaneand a portion of the butylenes havingboiling points in between those of normal butane and isobutane and abottoms fraction containing the butane and a portion of said butylenes,introducing the overhead along with the remainder of the four carbonatom fraction from the cracking stocks into the alkylation reactionzone, and controlling the proportion of isobutane to butylenes in' thereaction zone by regulation of the operation of said deisobutanizer.

a. In the alkylauon of isobutane-1n which a 'comprising introducingdirectly into said fractionating zone a portion of said first-mentionedmixture which contains olefin reactantsv higher bollino: than'saidisobutane in an amount at least eauivalent to the` excess of olennreactants in said mixture over the amount required to alkylate all thesaid'isobutane contained in said mixture whereby the isobutane contentoi' said material thus introduced directly into the fractionating zoneis included in the said fraction comprising unreacted isobutane andolefins equivalent in amount to said excess are included in said normalbutane fraction, and introducing the remainder of said ilrst-mentionedmixture into said alkylation reaction zone. whereby said excess ofisobutane in said reaction zone is maintained.

4. In the production of motor fuel by the alkylation of isobutane withlow-boiling. oleilns in an alkylation reaction zone in which low-boilingolens and an excess of isobutane are maintained in intimate contact'inthe presence of a catalyst and in which the hydrocarbon component of themixture leaving the reaction zone is thereafter separated from thecatalyst and subjected to fractionation to recover therefrom excessisobutane as an overhead fraction which is recirculated to thealkylation reaction zone, land in which at least a portion of themake-up Yisobutane is supplied in the form of hydrocarbon mixturescontaining isobutane and substantial proportions of low-boiling olefinshigher boiling than isobutane capable of alkylating` said isobutane, theamount of olefins present in said hydrocarbon mixtures exceeding thatrequired to alkylate all of the make-up isobutane available for saidalkylation, the improvement comprising supplying toI the alkylationreaction zone a rst portion of `said isobutane and olen-conrials, andoperating said fractionating zone to exclude said excess olens from thesaidoverhead isobutane fraction which is recirculated to thefractonating zone, whereby said excess of isobutane in said alkylationreaction zone is maintained.

EUGENE C. HERTHEL.

